In clinical practice, various types of image data are acquired from a patient and, if appropriate, processed further at a later point in time for the purpose of creating a finding or establishing a finding by a physician. These may be, inter alia, images that have been acquired by a computer tomograph, by an ultrasound device or by a nuclear spin device for example.
In image processing in the medical sector, large volumes of data have to be processed in order for an image, that can be further used, to be displayed. However, the procedure according to the invention can be used not only in the medical field but also in arbitrary other fields of application which are based on a postprocessing of image data.
In order that the acquired layer image data can be represented on a display device, they have to be transferred or converted—proceeding from their original two-dimensional form that is prescribed by the acquisition device—into a 3D representation form, so that a volume representation is possible on the display device. For this purpose, the collected layer images are computationally placed one above the other. The 3D representation thus obtained is then fed to further post processing methods.
These postprocessing methods for three-dimensional image data relate e.g. to contrasting the represented pixels in relation to one other or to the possibility of being able to adopt other observer perspectives for the respective object. Thus, it may be necessary, by way of example, to have not only the plan view of the lung but also a front view or to have displayed a section through a specific axis. The type of selected or applied postprocessing method(s) is defined in the application case and, in particular, by the treating physician.
Furthermore, the image data are often subjected to an application-case-specific representation method. Thus, the user may set or define so-called transfer functions that stipulate, for example, that specific structures are to be represented and others are not to be represented because they are not relevant in this case. Another setting that can be effected is that specific types of tissue are not to be represented as opaque, in order that the underlying layers are likewise visible. Thus, specific settings that are relevant to the representation of the image are made depending on the application case.
In the systems known from the prior art, all of the image data are first finally processed or converted before the postprocessing methods can be used. The previous procedure according to the prior art leads to the disadvantage that the user is exposed to high waiting times which—e.g. in an acute case—are unacceptable. A further disadvantageous effect lies in the fact that the user is also not informed about the current stage of calculation and is therefore compelled to wait for an unforeseeable time interval until the construction of the image is complete.
Scanners of CT and MR devices usually generate layer images which are then converted so that they image a three-dimensional volume. This three-dimensional image is then fed to further postprocessing methods, if appropriate.
In the known methods, a postprocessing method could only be employed after the volume data were completely loaded. In these known methods, it was very problematic that the user was repeatedly exposed to long waiting times. He therefore had to wait until the data had been completely loaded and only then could he use postprocessing methods, for the results of which he had to wait in some instances even longer and thus repeatedly.
In some medical applications, in particular, it may on the other hand have even been expedient and sufficient to prematurely interrupt an image construction process if e.g. at this point in time it was already foreseeable that only an image excerpt was of interest for the current issue in question.
A further known approach relates to the procedure of repeatedly calculating the three-dimensional images from the portion of the volume that has been loaded up to this point in time. However, the overall duration of the loading operation is lengthened considerably as a result of this.